Note that, the characteristic of FL is that only a portion of total clients are sampled as participant, and the participant clients have Non-IID local training data [1]}, [2]}, [3]}.
Therefore, the participant data are incomplete and biased.
We assume the participant data have a distribution different from the overall training data distribution of the learning task.
In particular, we assume the participant data are biased towards certain classes.
We sample a fraction of the data points in the participant data from a particular class in the overall training data and the remaining data points are sampled from the remaining classes uniformly at random.
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